A wind turbine blade comprises a load carrying structure which provides stiffness and rigidity to the construction of the blade. The load carrying structure is typically manufactured in a fibre reinforcing material. The fibre reinforcing material is often stacked forming a plurality of stacked fibre layers, while aligning an orientation of the fibres with the longitudinal direction of the load carrying structure in order to provide stiffness in the longitudinal direction. Today, the fibre layers are mostly selected from glass fibres or carbon fibres or hybrid material, and the design is chosen as a compromise considering both direct costs and performance in terms of overall weight and mass moment. A fibre layer made of a hybrid material comprises both carbon fibres and glass fibres. Glass fibres provide a different stiffness than carbon fibres. So a fibre layer made of a hybrid material with a static carbon fibre ratio gains in stiffness. However, the wind turbine blade may benefit from various degrees of stiffness and from various degrees of compression at various positions of the wind turbine blade, such as a root region, or a tip. A high carbon fibre ratio is advantageous towards the tip of the wind turbine blade to minimize deflection and reduce mass moment, while a high glass main laminate is advantageous in the root which experiences large compression straining.
There is a need for a method of manufacturing a wind turbine blade where the layup process may be simplified and for a blade where the variation in carbon fibre and glass fibre contents may be controlled and optimised to a higher degree.